Pipelines are generally the most economical way to transport large quantities of crude oil, refined oil products or natural gas over land. Steel pipes are commonly used, which can be subject to both internal and external corrosion. Corrosion protection is a critical process to ensure continuous pipeline operation.
Corrosion of oil transmission pipelines can result in leakage and large scale oil spills that are destructive of the ecosystem and pollute drinking water supplies (Sastri, Corrosion Inhibitors: Principles and applications, J. Wiley & Sons, New York, 2001, Ch 1, pp 5-30; Sacher, et al., J. Chromatogr, A, 1997, 764, 85-93; Zhao et al. Materials and Corrosion, 2004, 55, 684-688; Son, NACE International Corrosion Conference Series, 2007, 07618; Valentine, et al., Science, 2010, 330 208-211; Kujawinski, et al., Science & Technology, 2011, 45, 1298-1306; Thibodeaux, et al., Environmental Engineering Science, 2011, 28, 87-93; Bjorndal, et al., Science, 2011, 331, 537-538; and Atlas et al., Environmental Science & Technology, 2011, 45, 6709-6715). Corrosion is typically inhibited through addition to crude petroleum of oil-soluble heterocyclic compounds, such as quaternary ammonium salts and ionic liquids (Quraishi et al., Am. Oil Chem. Soc., 2000, 77, 1107-1111, Treybig et al., U.S. Pat. No. 4,957,640; Derek et al., U.S. Pat. No. 4,235,838; and Young et al., U.S. Pat. No. 6,645,399). Successful inhibition depends on the amount of inhibitor, and so measurement of inhibitor levels in crude oil is of great interest, especially in long-distance transfer pipelines (Nyborg et al., NACE-International, Corrosion Conference Series, 2012, 6, 4582-4590; Kvarekvål, NACE-International Corrosion, Conference Series, 2012, 6, 4329-4352; and Dugstad et al., NACE-International, Corrosion Conference Series, 2012, 5, 3573-3586).
Currently, no standard method exists for direct in-field monitoring of residual levels of corrosion inhibitors. Gas chromatography or high performance liquid chromatography combined with mass spectrometry (GC-MS or HPLC-MS) is the most widely adopted method for ex-situ quantification of residual corrosion inhibitors and other oil constituents. (Sacher et al., J. Chromatogr, A, 1997, 764, 85-93; Son, NACE International Corrosion Conference Series, 2007, 07618; Huhn et al., J. Anal. Chem., 1995, 351, 563-566; Gough et al., NACE-International, Corrosion, 98 paper, No 33; Schwartz et al., Anal. Chem., 1990, 62, 1809-1818; Chiang et al., Chemistry of Materials, 1992, 4, 245-247; Hsu, Anal. Chem., 1993, 65, 767-771; March, J. Mass Spectrom., 1997, 32, 351-369; and He et al., Energy Fuels., 2011, 25, 4770-4775). Although highly sensitive and specific, these methods are time consuming, requiring numerous sample purification and preparation steps prior to analysis. Due to the sample work-up required prior to analysis, samples need to be taken to the laboratory for analysis.